Piston ring



c. F. :ENGELHARDT 2,293,699 1 PISTON fame v Filed Oct. 21, 1940 4 Sheets-Sheet l 68 INVENTORQ' BY CARL EE GELHARDT' AT'IQRNEY.

Aug. 25, 1942. c. F2. ENGELHARDT PISTON RING 4 Sheets-Sheet 2 Filed 009. 21, 1940 F 5 M. A

i, W v

U U w 25% 5% INVENTOR. CARL F. ENGELHARDT Aug. 25, 1942.

' c. F. ENGELHARDT PISTON RING Filed Oct. 21, 1940 4 Sheets-Sheet 4 INVENT OR.

BY CARL E ENGELHARDT I fix, Y

ATTORNEY Patented Aug. 25, 1942 UNITED STATES 4 PATENT oF'FrcE PISTON RING Carl F. Engelhardt, Yeadon, Pa., assignor to Wilkening Manufacturing Company, Philadelphia, Pa., a corporation of Delaware 7 7 Application October 21, 1940, Serial No. 362,120

6 Claims. ((31. ao9 45 tween the sectors, and spring means forming an integral part of the piston ring and also preferably formed of the same sheet metal of which the cylinder-contacting elements are formed,

Figure 2. 1 Figure 4 represents a section on line 4-4 of Figure 2.

Figure represents a sectional view of the upper portion of a piston showing the piston ring of the present invention, disposed in each of the three ring-receiving grooves thereof.

thereby to tend to expand the ring tangentially or circumferentially with a resultant radially outward expansion of the component cylindercontacting elements thereof.

The present application is a continuation-inpart of applicant's co-pending application Serial No. 321,200, filed February 28, 1940.

The piston ring of the present invention may be used both for oil control purposes in the bottom ring-receiving groove of a piston which has apertures through the piston wall for oil drainage and which may also be used. in the upper ring-receiving grooves without any oil drain holes through the piston wall, for compression purposes.

For the purpose of illustrating the invention, there are shown in the accompanying drawings forms thereof which are at present preferred, since the same have been found in practice to give satisfactory and reliable results, although it is to be understood that the various instrumentalities of which the invention consists can be variously arranged and organized and that the invention is not limited to the precise arrangement and organization of the instrumentalities as herein shown and described.

In the accompanying drawings in which like reference characters indicate like parts,

Figure 1 represents a top plan view of a piston ring embodying the present invention, as shown installed in a piston disposed'within a cylinder, which is generally on line [-4 of Figure, 3 (the parts not being in true proportion, for'purposes of better illustration).

Figure 2 is a perspective view of a fragmentary portion of the piston ring of the present invention on a much enlarged scale, showing the construction of the radially-inwardly-extending spring loops.

U-shaped spring members 5|. v Figures 9 and 10 represent a front elevational blank for the formation of another embodiment Figure 6 represents a perspective view of a fragmentary portion of a sheet metal blank in its iiat condition of which the piston ring of the present invention may be'formed, but before the cylinder-contacting elements 22' and 23 have been bentover and before the spring-forming elements 25 have been formed or shaped into the springs 5| intervening ,the ing elements 22 and".

Figures '2 and 8 represent a front view and a top elevational view, respectively, of a fragmentary portion of a strip of piston ring material like that shown in Figure 6, but after the cylinder-contacting elements: '22 and 23 have been bent over and after the intervening springforming portions 25 have been formed into the generally U-shaped springs 5|, but before the strip has been completely formed into the armate formation by the further collapsing of the view and a top plan view, respectively, similar to that shown in Figures 7 and 8, but after the strip had been formed into generally arcuate' form corresponding generally to the curvature of the cylinder in which the piston ring is to be,

of the present invention.

Figure 12 represents a perspective view similar to that of Figure 2 of in Figure 11. I

Figure 13 represents a perspective view similar to that of Figure 6, showing a sheet metal blank for the formation of still another embodiment of the presentinvention.

Figure 2-A represents a perspective view of Figure 14 represents a perspective view sim cylinder-contactthe embodiment indicated ilar to that of Figure 2 of the embodiment indicated in Figure 13. s Figure 15 represents a perspective view, similar to that of Figure 6 showing a sheet metal blank for the formation of another embodiment 5 Figure 1'7 represents a perspectiveview siml0 ilar to that of Figure 6 showing a sheet metal blank for the formation of yet another embodiment of the present invention.

Figure 18 represents a perspective view similar tothat of Figure 2 of the embodiment indiit cated in Figure 17.

One form or embodiment of the present invention is illustrated in Figures 1 to inclusive, the

-formation of which is illustrated in Figures 6 to 10 inclusive. 20,

Thus, in this embodiment oi the present invention, a flat sheet-metal strip 22 of suitable thickness having an aggregate width 2!, is cut out in the general manner indicated in Figure 6,,

to form juxtaposed upper and lower generally 25 sector-shaped cylinder contacting elements 22- and 22 with intervemng connectin spacer portions 24 and with spring-forming portions 22.

.The connecting spacer portions 24 maybe perforated by providin openings 22 therein for oil drainage through the piston ring after it is nnally formed, such apertures being advantageous when the piston ring is used for oil control purposes in one or two of the lower rin -receivin grooves 21 of a three-groove piston such as illustrated in Figure 5, or of a? four-groove piston wherein the lowermost or the lower two ringreceiving grooves are provided with oil drain holes 22 extending through the piston wall 22 for oil draining purposes. When used for compression purposes in the uppermost ring-receiving groove 22 of the piston 2| or in the upper two ringreceiving grooves 20 and 22 (Figure 5), the holes 22 may beomitted although they may also be retained when the piston ring is for such compression purposes in the upper ring-receiving grooves. In addition to cutting out the metal in the spaces 22 and 24 intervening the cylinder-contacting elements 22 and 22 respectively, the cylinder-contacting elements 22 and 22 are also preferably partly severed from the connecting spacer portions 24 by fracturing the metal along lines 22 and 22 more or less parallel .to or in line with the edges 21 and 22 from the corners 22 and 42; to a suitable extent so that the springforming portions 25 of the sheet metal strip 22 may be more freely formed into the generally U-shaped springs ii without interference from or binding by the cylinder-contacting elements 22 and 22.- so

The longitudinal 6r circumferential width of the cylinder-contacting portions 22 and 22 is slightly smaller in the base dimension 42 than the juxtaposed edges 44 and will parallel each other and will be disposed as radii in relation to the axis or centre 42 of the piston. The peripheral or cylinder-contacting edges or surfaces 41 and 42 of the cylinder-contacting elements 22 and 22, respectively, may also be Is given a slight. convex arcuate curvature between the ends 42 and 22 thereof corresponding to the curvature of the cylinder in which the piston inder-contacting surfaces 41 and 42, respectively,

will form corresponding true circles matching the 1 circle of the cylinder.

The formation of the blanks shown in Figure 6 may be accomplished by Punching operations on any suitable punch press, either manual or semiautomatic or fully automatic,-wlth suitable dies and punches either by step-by-step or progressive punching operations. However, if desired, the blanks shown in Figure 6 may also be formed by milling out the portions 22 and 24 or by cutting out the portions 22 and 24 on a shaper or on a broaching machine. If the portions 22 and 24 are to be cut out on a milling machine or on a shaper or on a broaching machine, several sets may be stacked together andmay be milled, shaped or broached all together, gang-wise. 4

The piston ring is formed by bending overtowards each other the juxtaposed cylinder-conments 22 in a generally radial direction to form aseries of spaced corrugation-like or loop-like springs ii of an axial dimension 42 generally corresponding to the distance between the inner flat surfaces of the cylinder-contacting elements 22 and 22 when bent into their final form as indicated in Figures 3 and 2.

In its final form, the piston ring thus formed will consist of a central corrugated annulus of alternating flattened crests 24 and rounded blank shown'in Figure 6 may be accomplished by successive bending operations performed in any suitable sequence or -all the bending operations may be done more or less simultaneously to produce the result indicated in Figures 9, 10, l and 2.

In Figures 7, 8,9 and 10, however, I have illustrated what may be one desirable sequence of bending or forming operations, although it is to be understood that this sequence may be changed, or the bending or forming operations may all be accomplishedmore or less simultaneously by suitable automatic or semi-automatic bending and forming jigs or fixtures or machines.

Thus, for instance, in Figures 7 and 8, I have illustrated what may be an initial stage in the formation of the piston ring wherein the cylindercontacting elements 22 and 22 have been bent over to parallel each other and wherein thes'pring-forming portions 22 have been'bent into aninltial U-shape formation 22 preliminary to their formation into the more close loop-shaped spring "shown in Figures 9 and 10. In this condition, the piston ring forming strip would be generally straight as indicated particularly in Figure 8,-with the juxtaposed edges 44 and 42 substantially separated from each other and in non-parallel relation. Thereafter, the generally U-shaped formations 22- may be collapsed some-, what to form the more or less loop-like springs In the commercial manufacture of piston rings according to th present invention, the blank shown in Figure 6 as well as the corresponding piston ring strips shown in Figures .7, 8, 9 and 10 may be formed more or less continuously in relatively great lengths from which smaller pieces may then be cut off after the strip has been completely formed or shaped into the form shown in Figures 7 and 8, or even after it has been formed into the curved shape shown in Figures 9 and 10. The length of the individual pieces would correspond more or less accurately to the circumferential dimension of the piston ring desired. For the different size piston rings the other dimensions would also be'varied to accord with the width of the ring-receiving groove, the depth of the ring-receiving groove, and diameter of the piston.

Thus, for instance, the individual pieces corresponding to the circumferential length of the piston ring could be cut off while the strip is straight as in Figures 7 and 8 and then the shorter piece curved and completed to the form shown in Figures 9 and 10 and in Figures land 2, or the strip can be curved while it is still part ofthe whole piece of considerable length and formed into a generally spiral formation as it is being. curved and thereafter individual pieces cut off corresponding to the circumferential length of the piston ring so that each piece will be one complete circle of the desired diameter.

In making the piston ring, the springs 5| or the corrugations are collapsed until the juxtaposed edges 44 meet each other or abut each other and until the edges 45 likewise meet and abut each other, thereby producing the curved shape. However, when the compression pressure is released the :springs 5| or. corrugationsopen up slightly or spring back slightly so that the edges 44 and 45 separate from each other slightly as indicated in Figures 2, 9 and 10. However, the circumferential length of the piston ring is so adjusted that when the free ends 56 and 51 of the piston ring abut each other and the rin is compressed circumferentially or tangentially into the diameter of the cylinder 58, the radial edges 44 and 45 of the cylinder-contacting elements 22 and 23, respectively, will generally abut each other or will have but a very small clearance between them. It is estimated that the total or'aggregate of all clearances between the successive pairs of edges 44 in the entire circumference or between the successive pairs of edges 45 in the entire circumference may be a few thousandths of an inch, perhaps .003 to .007", more or less (that is, an amount perhaps no greater than the clearance at the gap in an or-. dinary piston ring; is being understood that at the gap or break, 68 there would be substantially no clearance as the edges 56 and 51 will abut each other. Thus, by reason of the fact that each of the bends or corrugations or springs 5i tends to open. up slightly when the ring is compressed into the cylinder as is indicated in Figure 1, there is a uniformly distributed tangential or circumferential force between successive sections of the piston ring, that is; between successive or adjacent cylinder-contacting elements 22 and 23, respectively, and this force is inturn translated into an outward radial component force tending to press the cylinder-contacting edges 41 .and 48 thereof, into contact with the cylinder wall with auniformly distributedand predetermined radial force.

he cylinder-contacting elements 22 and 23 are preferably (though not necessarily) staggered slightly or offset slightly in relation to each other as indicated particularly in Figures 6, 'I, 8, 9 and 10, so that the edges 44 and edges 45 are not directly in alignment with each other but are slightly offset in relation to each other, thereby tending to minimize even any tendency to blow-by.

In the manufacture of the piston ring of the present invention, I may also grind-finish the cylindrical periphery 59 of the completed .ring by clamping the finished ring axially between suitable supporting discs upon a suitable mandrel or any suitable fixture, while the'ring isgenerally fully compressed, and then grinding the periphery 59 to match the cylinder, by rotating the ring about its axis against a revolving grinding wheel. Ifdesired, a number of piston rings may be so clamped and held side by side on the same fixture or on the same mandrel between the same clamping discs or blades, so that they may be ground all together to match the cylinder. i

The gap or break in the piston ring may be formed through the pair 'of juxtaposed cylindercontacting elements 22 and 23 as indicated in- Figures 1 and 2.

The piston ring of the present invention is preferably made of sheet steel of suitable consistency or suitable hardness although it may be made of other sheet metals, such as sheet bronze or sheet brass or other suitable alloys, both fer-v rous and non-ferrous. If the piston ring is made out of sheet steel, it may be formed out o'f fully tion shown in Figures 7 and 8 and even the formation shown in Figures 9 and 10 may be made while the metal is fully annealed, although'these formations may also be formed with a certain amount of hardness set into the metal by suitable hardening and tempering. The

be done before the cylinder-contacting circumference of the completed ring is grind-finished or otherwise finished to the cylinder diameter.

Another embodiment of the present invention is shown in Figures 11 and 12 in which the central corrugated annulus is relatively narrower andin which the crests 24 are solid and m-:e rounded and have a smaller circumferential di-- mension than the cylinder-contacting elements 22 and 23, notches 35a and 35a replacing slits 35 and 35.

Figures 13 and 14 show another embodiment in which the cylinder-contacting elements 22 and 23 are given a generally L-shaped coniigu ration in the sheet metal blankshown in Figure 13 with the base of the L of the element 22 exfinal hard-. ening and tempering, however, should preferably tending in the direction opposite that of the element 23 so that, in the flnal ring, as shown in Figure 14, the staggering of the cylinder-com tacting elements 22 and 23 is much more accentuated-than shown in Figures 2, 8, '1, 8, 9 and 10. This formation is especially eflective in minimizing any tendency to "blow-by."

Figures and 16 show another embodiment in bottom walls and a back and generally sinuous loops of spring metal connecting the side edges of adjacent back walls, said loops projecting radially inwardly froms'aid sections and being of an axial width not more than two-thirds I which the members or troughs ii are displaced bers Ma and Si b need not be parallel or placed in the relative positions shown.

In any of the embodiments shown, it is possible to make one of the cylinder-contacting elements 22 or 23 with a radially smaller dimension or'to omit it completely. In such a case, each piston ring would present only a single narrow annular rib making contact with the cylinder; the springmembers 5| .then acting as a supporting ring and spacing ring.

The piston ring of the present invention is highly effective both for oil control and for compression, and may be used without any separate expander spring and will produce a suitably high cylinder-contact pressure per unit of area between the cylinder-contacting surfaces of the piston ring and the cylinder wall, without, however,

the axial width of the piston ring, and said spring loops being displaced from the central plane of the piston ring. l

3. A one-piece, flexible, circumferentially-expanding folded sheet-metal piston ring comprising a central, corrugated annulus composed of alternating crests and troughsof spring sheet metal, with the direction from crest to trough being generally radial, said troughs being radially innermost in relation to the crests and being continuously curved in cross-section at their hottoms, and said crests being radially outermost in relation to said troughs, a pair of more or less parallel integrally formed extension's'proiecti'ng from each of said crests radially outwardly therefrom, said extensions being arranged in close proximity to each other to form a pair of more or less continuous, annular, axially displaced, cylinder-contacting ribs, said troughs being relatively narrow spring members axially displaced from the center plane of said ring, successive spring,

members being alternately above and below the center plane of said ring.

4. A one-piece, flexible, circumferentially-expanding folded sheet-metal piston ring comprising a series of sections each consisting of top and bottom walls and a back wall and generally sinuous loops of spring metal connecting the side producing an excessive pressure which will result in a scoring of-the cylinder wall.

The present invention may be embodied in other specific forms without departing from the spir- I it or essential attributes thereof, and it is therefore desired that the present embodiments be considered in all respects as illustrative and not restrictive, reference being had to the appended claims ratherthan to the foregoing description to indicate the scope of the invention.

Having thus described the invention; what is hereby claimed as new and desired to be secured by Letters Patent is:

l. A one-piece, flexible, circumferentially-exe panding folded sheet-metal piston ring comprising a central, corrugated annulus composed of alternating crests and troughs of spring sheet metal, with the direction from crest to trough being generally radial, said troughs being radially innermost in'relation to the crests and being continuously curved in cross-section at their boting aseries of sections each consisting of toms, and said crests being radially outermost in relation to said troughs, a pair'of more or less edges of adjacent back walls, said loops projecting radially inwardly from said sections and being of an axial width not more than two-thirds the axial width of the piston ring, and said spring loops being displaced from the central .plane of the piston ring, successive spring loops being alternately above and below the center plane of said piston ring.

5. A one-piece, flexible, circumferentially-expanding folded sheet-metal piston ring comprising a central, corrugated annulus composed of alternating crests and troughs of spring sheet metal, with thedirection from crest to trough being generally radial, said troughs being radially innermost in relation to the crests and being continuously curved in cross-section at their bot-' toms, and said crests being radially outermostin relation to said troughs, a pair of more orless parallel integrally formed extensions projecting from each of said crests radially outwardly thereparallel integrally formed extensions projecting.

' from, each of said crests radially outwardly there- 'from, said extensions being arranged in close proximity to each other to form a pair of more or less continuous, annular, axially displaced, cylinder-:contacting ribs, said troughs being relative- 1y narrow spring members axially displacedifrom the center plane of said ring.

2. A one-piece, flexible, circumierentially-ex panding folded sheet-metal piston ring compristop and from, said extensions being arranged in close proximity to each other to form a pair of more or less continuous, annular, axially displaced,'cylinder-contactingi-ribs, said troughs being relatively narrow axially-separated twin spring members axially displaced from the center plane of said ring.

6. A one-piece, flexible, circumferentially-ex panding folded sheet-metal piston ring comprising a series of sections each consisting of top and bottom walls and a back wall and generally sinuous axially-separated twin loops of spring metal connecting the side edges of adjacent back walls, said loops projecting radially inwardly from said sections and being of an axial= width not more than two-thirds the axial width of the piston ring, and said spring loops being displaced from the central planeoi the pistonring. i V

CARL l". ENGELHARDT. 

